CN107817258B - Liquid silicone rubber aging degree evaluation method based on X-ray diffraction spectrum peak-splitting fitting - Google Patents

Abstract

A method for assessing the aging degree of liquid silicone rubber based on X-ray diffraction pattern peak fitting is disclosed, with the following specific steps: 1S. Samples are taken from the liquid silicone rubber to be tested. 2S. X-ray diffraction analysis is performed on the sample. Peak fitting is performed on the X-ray diffraction patterns of the inner and outer layers. The ratio of the integrated areas of the corresponding diffraction peaks of PDMS and silica is calculated. This ratio is compared between the outer and inner layers to determine the aging degree of the liquid silicone rubber. The ratio of the integrated areas of the corresponding diffraction peaks of silica and PDMS is denoted as XSiO2/PDMS. 3S. The aging degree of the sample is determined. The advantage is that it provides a more accurate assessment of the aging degree of liquid silicone rubber materials in power plant equipment, improves the equipment aging assessment procedure, and lays the foundation for the operation and maintenance department to formulate reliable maintenance strategies.

Description

An evaluation of the ageing degree of liquid silicone rubber based on peak fitting of X-ray diffraction patterns estimation method

technical field

The invention relates to the technical field of material performance evaluation, in particular to a method for evaluating the aging degree of liquid silicone rubber based on peak-part fitting of an X-ray diffraction pattern.

Background technique

Silicone rubber is a composite insulating material commonly used in power systems. It is widely used in the field of high-voltage external insulation. Liquid silicone rubber is a relatively high-grade silicone rubber developed since the 1970s. It is characterized by: vinyl siloxane The addition reaction with the silicon hydrogen group completes the crosslinking; the molecular weight is small, the viscosity of the rubber compound is low, and it is easy to process and shape; it can be vulcanized at room temperature, or the temperature can be increased to accelerate the vulcanization. Compared with condensed silicone rubber, it also has the characteristics of deep vulcanization, no by-products, and small shrinkage.

Liquid silicone rubber has been widely used as the outer insulating sheath of the transformer in the 110kV ~ 500kV substations of the State Grid and China Southern Power Grid. In recent years, the liquid silicone rubber outer insulating sheath used in some areas of China Southern Power Grid has experienced serious aging phenomena such as hydrophobicity decline, cracking, and chalking, which greatly affects the normal operation of the equipment. Therefore, by detecting various performance parameters of liquid silicone rubber and accurately evaluating its aging state, it has important guiding significance and engineering value for the operation and maintenance of power station equipment.

X-ray diffraction analysis is a method of analyzing the crystal structure, parameters and defects of materials by using the diffraction phenomenon of X-rays in crystals. The main component of liquid silicone rubber is polydimethylsiloxane (PDMS), and contains more silica filler. Due to its excellent performance, liquid silicone rubber generally does not need to add aluminum hydroxide filler to improve the tracking resistance. The composition of silica filler is similar to the siloxane backbone, so it is difficult to completely distinguish the two in elemental and functional group analysis. However, in the XRD diffraction pattern, the peak positions of silica filler and siloxane are different, which can be distinguished by peak fitting.

In the aged liquid silicone rubber, the side chain organic groups of PDMS are oxidized, and the cross-linking is increased, which is reflected in the obvious decrease in the content of organic components, while the inorganic components (including silica fillers and SiO-like SiO2 in the cross-linked structure of PDMS) structure) content increased. The integrated intensity of diffraction peaks of XRD is proportional to the content of the corresponding phase. Therefore, the integrated intensity of diffraction peaks of PDMS and silica can be calculated through peak fitting, so as to quantitatively analyze the composition of liquid silicone rubber materials and help the maintenance department more accurately. Assess the degree of aging of materials to formulate corresponding operation and maintenance strategies.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the shortcoming of the above-mentioned prior art, provide a kind of X-ray diffraction pattern based on the X-ray diffraction pattern of analyzing the composition change of the liquid silicone rubber surface layer by analyzing the X-ray diffraction pattern of the liquid silicone rubber surface layer. The comprehensive evaluation method for the aging degree of liquid silicone rubber, the test method is suitable for the detection test and aging degree evaluation of liquid silicone rubber material without aluminum hydroxide filler.

The present invention is achieved through the following technical solutions:

A method for evaluating the aging degree of liquid silicone rubber based on X-ray diffraction pattern peak fitting, the specific steps are as follows:

1S Take a sample from the liquid silicone rubber to be tested.

2S performs X-ray diffraction analysis on the sample, performs peak fitting on the X-ray diffraction patterns of the inner layer and the surface layer, calculates the ratio of the integral area of the diffraction peaks corresponding to PDMS and silica, and compares the ratio between the surface layer and the inner layer, Thus, the aging degree of the liquid silicone rubber can be judged; the ratio of the integral area of the corresponding diffraction peaks of silica and PDMS is recorded as X _SiO2/PDMS :

Among them, A(SiO2) is the integrated area of the peak corresponding to silica after peak separation, the abscissa of the center of the peak is located at 2θ=22±0.1°, A(PDMS) is the integrated area of the peak corresponding to PDMS after peak separation, and the peak The center abscissa of is located at 2θ=12±0.1°.

3S judges the degree of aging of the sample, the ratio of X _SiO2/PDMS of the surface layer and inner layer of the sample X _outer/in = X _{SiO2/PDMS outer} /X _{SiO2/PDMS inner} , when X _outer/in > 1.5, it is determined that the sample occurs Serious aging requires repair or replacement measures; when 1.5>Xout _/in >1, it is determined that the sample is slightly aging, and further evaluation needs to be combined with other testing methods; when Xout _/in = 1, it is determined that the liquid silicone rubber Aging has not occurred.

As an improvement of the above scheme, the sampling from the liquid silicone rubber to be detected in step 1 is to use a non-woven fabric dipped in absolute ethanol to clean the sample from the liquid silicone rubber sheath to be detected with a scalpel. For the contamination attached to the surface of the sample, after the anhydrous ethanol has evaporated, cut a sample with a length and width of about 1cm*1cm and a thickness of 1 to 2mm from the surface layer and inner layer of the sample for X-ray diffraction analysis.

As an improvement of the above scheme, the X-ray diffraction pattern described in step 2 should be preprocessed before the peak-split fitting, and the specific steps are as follows:

2.1S read the X-ray diffraction pattern, PDMS has an amorphous dispersion peak at the diffraction angle 2θ=12±0.1° in the spectrum, and silica has an amorphous dispersion peak at the diffraction angle 2θ=22±0.1° in the spectrum.

2.2S Adjust the baseline of the spectrum, so that the bottom of the spectrum coincides with the baseline more smoothly and completely, and deduct the part below the baseline to obtain more accurate diffraction peak data.

In 2.3S, sub-peak fitting was performed on the diffraction peak data.

The present invention has the following beneficial effects: the present invention relates to a new method for evaluating the aging degree of liquid silicone rubber based on X-ray diffraction pattern peak fitting, which can provide more accurate liquid silicone rubber materials for power station equipment in combination with existing evaluation methods The aging degree assessment of the equipment is completed, and the aging assessment procedure of the equipment is improved, so as to lay the foundation for the inspection department to formulate a reliable maintenance strategy.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the surface layer of the liquid silicone rubber surface layer sample in the embodiment.

Fig. 2 is the X-ray diffraction pattern of the inner layer of the liquid silicone rubber surface layer sample in the embodiment.

Detailed ways

Example

A method for evaluating the aging degree of liquid silicone rubber based on X-ray diffraction pattern peak fitting, the specific steps are as follows:

1S Take samples from the liquid silicone rubber to be tested; use a scalpel to take samples from the liquid silicone rubber sheath to be tested, and then use a non-woven fabric dipped in absolute ethanol to clean the dirt attached to the surface of the sample, and wait for the absolute ethanol to evaporate. After completion, cut out samples with a length and width of about 1cm*1cm and a thickness of 1 to 2mm from the surface layer and inner layer of the sample for X-ray diffraction analysis.

2S As shown in Figure 1 and Figure 2, read the X-ray diffraction pattern, PDMS appears in the pattern at a diffraction angle of 2θ=12±0.1°, and an amorphous dispersion peak appears, while silica appears in the pattern at a diffraction angle of 2θ=22±0.1° Amorphous dispersion peaks.

3S adjusts the baseline of the spectrum, so that the bottom of the spectrum coincides with the baseline smoothly and completely, and the part below the baseline is deducted to obtain more accurate diffraction peak data.

4S, perform peak fitting on the X-ray diffraction patterns of the inner and outer layers, and calculate the difference between PDMS and silica.

The ratio of the integral areas of the diffraction peaks should be compared to the ratio of the surface layer and the inner layer to judge the aging degree of the liquid silicone rubber; the ratio of the integral areas of the corresponding diffraction peaks of silica and PDMS is recorded as X _SiO2/PDMS :

Among them, A(SiO2) is the integrated area of the peak corresponding to silica after peak separation, the abscissa of the center of the peak is located at 2θ=22±0.1°, A(PDMS) is the integrated area of the peak corresponding to PDMS after peak separation, and the peak The center abscissa of is located at 2θ=12±0.1°.

5S judges the degree of aging of the sample, the ratio of X _SiO2/PDMS of the surface layer and inner layer of the sample X _outer/in = X _{SiO2/PDMS outer} /X _{SiO2/PDMS inner} , when X _outer/in > 1.5, it is determined that the sample occurs Serious aging requires repair or replacement measures; when 1.5>Xout _/in >1, it is determined that the sample is slightly aging, and further evaluation needs to be combined with other testing methods; when Xout _/in = 1, it is determined that the liquid silicone rubber No aging occurred. According to the samples detected in Figure 1 and Figure 2, the results obtained are as follows in Table 1:

Xouter _/inner =1.840>1.5, it is judged that the sample is severely aged and needs to be repaired or replaced.

The above detailed description is a specific description of a feasible embodiment of the present invention, and the embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification without departing from the present invention should be included in the patent scope of this case middle.

Claims (2)

1. A liquid silicone rubber aging degree evaluation method based on X-ray diffraction spectrum peak-splitting fitting is characterized by comprising the following specific steps:

1S, sampling from liquid silicone rubber to be detected;

2S, carrying out X-ray diffraction analysis on the sample, carrying out peak-splitting fitting on the X-ray diffraction maps of the inner layer and the surface layer, calculating the ratio of the integral areas of corresponding diffraction peaks of PDMS and white carbon black, and comparing the ratio of the surface layer and the inner layer so as to judge the aging degree of the liquid silicone rubber; the ratio of the integral areas of the corresponding diffraction peaks of white carbon black and PDMS is marked as X_SiO2/PDMS：

Wherein, a (SiO2) is the integrated area of the peak corresponding to the white carbon black after peak separation, the central abscissa of the peak is located at 22 ± 0.1 ° 2 θ, a (PDMS) is the integrated area of the peak corresponding to PDMS after peak separation, the central abscissa of the peak is located at 12 ± 0.1 ° 2 θ, an X-ray diffraction pattern is read, an amorphous dispersion peak appears at a diffraction angle of 12 ± 0.1 ° 2 θ of PDMS in the pattern, an amorphous dispersion peak appears at a diffraction angle of 22 ± 0.1 ° 2 θ of white carbon black in the pattern, the pattern base line is adjusted to enable the whole bottom of the pattern to be smoothly and completely coincided with the base line, a part below the base line is deducted to obtain accurate diffraction peak data, and the diffraction peak data is subjected to peak separation fitting;

3S, judging the aging degree of the sample, namely the surface layer and the inner layer X of the sample_SiO2/PDMSRatio X of_Outer/inner＝X_{SiO2/PDMS outer layer}/X_{SiO2/PDMS inside}When X is present_Outer/innerWhen the temperature is higher than 1.5, judging that the sample is seriously aged and needing to take repairing or replacing measures; when 1.5 > X_Outer/innerWhen the temperature is higher than 1, judging that the sample is slightly aged, and further evaluating by combining other detection means; when X is present_Outer/innerWhen the silicone rubber is aged 1, it is judged that the liquid silicone rubber is not aged.

2. The method for evaluating the aging degree of the liquid silicone rubber based on the peak fitting of the X-ray diffraction pattern according to claim 1, wherein the step 1 is to sample the liquid silicone rubber to be detected, after sampling the liquid silicone rubber to be detected from the liquid silicone rubber sheath by a scalpel, the non-woven fabric dipped with absolute ethyl alcohol is used for cleaning dirt attached to the surface of the sample, and after the absolute ethyl alcohol is volatilized, sample pieces with the length of about 1cm X1 cm and the thickness of 1 to 2mm are cut from the surface layer and the inner layer of the sample to perform X-ray diffraction analysis.

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